System and method for designing a customized switched metro Ethernet data network

ABSTRACT

A method for automatically designing a switched metro Ethernet data is provided. During execution of the method, data network information, customer demand information, equipment information, and at least one design constraint is received. Based thereon, a potential topology design for the switched metro Ethernet data network is automatically established. The potential topology for the switched metro Ethernet data network can be a tree topology that is rooted at a predetermined hub node and that has a plurality of leaves. Each leaf is located at a customer location. In a particular embodiment, an aggregation node is placed at the hub node. Further, an aggregation node is placed at a predetermined redundant hub node. Additionally, an aggregation node is placed at another location in the tree topology.

FIELD OF THE INVENTION

The present disclosure relates generally to the design of switched metroEthernet data networks.

BACKGROUND

Ethernet is a local-area network architecture that was developed in thelate 1970s for use in offices, e.g., to interconnect computers to eachother and to a common printer. In recent years, companies have begun todevelop ways to expand Ethernet principles to wide area networks, e.g.,using Internet routers that are interconnected in various ways. Theresult has been the creation of switched metro Ethernet data networks.

Depending on the topology used, finding the most optimal topology for aswitched metro Ethernet data network can be NP-complete and can only besolved via an exhaustive search. Performing such an exhaustive search isimpractical since the time of the search increases exponentially as thesize of the data network increases. As a result, methods for designingswitched metro Ethernet data networks typically utilize a manualper-network approach to establish a data network design. This manualapproach can be time consuming, expensive, and can result in inefficientnetwork designs.

Accordingly, there is a need for an improved system and method fordesigning a customized switched metro Ethernet data network.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is pointed out with particularity in the appendedclaims. However, other features are described in the following detaileddescription in conjunction with the accompanying drawings in which:

FIG. 1 is a diagram of an exemplary customized switched metro Ethernet(CSME) data network;

FIG. 2 is a diagram of a tree topology for the CSME data network;

FIG. 3 is a diagram of an exemplary system for designing a CSME datanetwork;

FIG. 4 is a flow chart to illustrate an exemplary method for designing aCSME data network;

FIG. 5 is a flow chart to illustrate a method for locating a multicasttree;

FIG. 6 is a flow chart to illustrate a method for determining where toplace aggregation nodes in the multicast tree; and

FIG. 7 is a flow chart to illustrate a method for adding redundancy tothe multicast tree.

DETAILED DESCRIPTION OF THE DRAWINGS

A method for automatically designing a switched metro Ethernet data isprovided. During execution of the method, data network information,customer demand information, equipment information, and at least onedesign constraint is received. Based thereon, a potential topologydesign for the switched metro Ethernet data network is automaticallyestablished.

In a particular embodiment, the potential topology for the switchedmetro Ethernet data network is a tree topology that is rooted at apredetermined hub node and that has a plurality of leaves. Each leaf islocated at a customer location. In a particular embodiment, anaggregation node is placed at the at the hub node. Further, anaggregation node can be placed at a predetermined redundant hub node.Additionally, an aggregation node is placed at at least one otherlocation in the tree topology.

In a particular embodiment, a first cost of placing an aggregation nodeat the other location in the tree topology is determined. Also, a secondcost of connecting other locations in the tree topology to the parentnode of an aggregation node that could potentially be placed at thislocation is determined. An aggregation node is placed at this locationin the tree topology when the second cost is greater than the firstcost.

Further, in a particular embodiment, an availability value is computedfor each aggregation node in the tree topology other than the hub nodeand the redundant hub node. A redundant path is added from theaggregation node to the hub node when the availability value is lessthan a predetermined threshold. The redundant path can be added bydetermining a first path from a particular node to the parent node ofthe particular node and connecting the particular node to a next closestnode other than the parent node by a second path that is different fromthe first path.

In a particular embodiment, an aggregation node-to-aggregation node linkis sized by dividing an aggregate customer bandwidth by a concentrationratio. Further, a detailed configuration of each aggregation node isdetermined. Thereafter, a cost of the potential topology of the switchedmetro Ethernet data network is determined. The cost of the potentialtopology can then be output for use, e.g., by a network engineer.

In another embodiment, a method for designing a switched metro Ethernetdata network is provided. Using the method, a non-redundant treetopology for a switched metro Ethernet data network is established atleast partially within a set of existing nodes. Based on an availabilityconstraint, one or more redundant connections can be added to the atleast one non-redundant tree topology.

In yet another embodiment, a system for designing a switched metroEthernet data network is provided and includes a computer processor anda computer readable memory that is accessible to the computer processor.A computer program for designing a switched metro Ethernet data networkcan be embedded within the memory. In this embodiment, the computerprogram includes instructions to receive one or more user inputs relatedto the switched metro Ethernet data network. Further, the computerprogram includes instructions to generate a non-redundant tree topologyfor the switched metro Ethernet data network at least partially based onthe one or more user inputs. The computer program also includesinstructions to add one or more redundant connections to thenon-redundant tree topology to create a design. Additionally, thecomputer program includes instructions to output at least one designoutput related to the design.

In still another embodiment, a switched metro Ethernet data network isprovided and includes at least one hub node. A plurality of customernodes is connected to the hub node to establish a tree topology. In thisembodiment, a design of the tree topology is generated using a switchedmetro Ethernet data network design tool. Further, the switched metroEthernet data network design tool includes instructions to generate anon-redundant tree topology for the switched metro Ethernet data networkat least partially based on one or more user inputs and instructions toadd one or more redundant connections to the non-redundant tree topologyto create the design.

Referring to FIG. 1, a customized switched metro Ethernet (CSME) datanetwork is shown and is designated 100. As illustrated in FIG. 1, theCSME data network 100 includes an aggregation layer 102 and an accesslayer 104. In a particular embodiment, the access layer 104, a.k.a.,provider edge—customer location equipment (PE-CLE), provides theinterface to a customer at the customer's location. Further, in aparticular embodiment, the aggregation layer 102, a.k.a., provideredge—point of presence (PE-POP), aggregates incoming traffic 106 fromthe access layer 104 and forwards outgoing traffic 108 to the accesslayer. The CSME data network 100 can provide virtual private local areanetwork (LAN) connection, e.g., point-to-point, point-to-multipoint, andmultipoint-to-multipoint, between customer sites.

As indicated in FIG. 1, the aggregation layer 102 can include aplurality of aggregation nodes 110. In an illustrative embodiment, theaggregation nodes 110 can include data communication equipment (DCE),such as any of the 7600 series Internet routers by Cisco, that can beused to route, switch, or otherwise transmit data packets between theaggregation nodes 110. The access layer 104 can include a plurality ofaccess nodes 112. In an illustrative embodiment, the access nodes 112can include data termination equipment (DTE), i.e., one or more devicesthat are the source or destination of data packets.

In a particular embodiment, the aggregation nodes 110 can provideinterfaces to the access nodes 112 and other aggregation nodes 110. Inan illustrative embodiment, the aggregation nodes 110 can beinterconnected in a tree fashion, as shown in FIG. 2, in order to routedata traffic between the aggregation nodes 110 and the access nodes 112connected thereto. If data traffic is between two access nodes 112 thatare connected to the same aggregation node 110, the data traffic isrouted or switched between the two access nodes 112 via that particularaggregation node 110 to which those access nodes 112 are connected.

In a particular embodiment, the aggregation layer 102 includes a hubnode 114, e.g., a node in a central office, and a redundant hub node116, e.g., another node in a central office. Further, in a particularembodiment, the CSME data network 100 can have a tree topology, shown indetail in FIG. 2, that is rooted at the hub node 114, unlessavailability requirements require some of the aggregation nodes 110 tohave redundant connections, i.e., connections to the redundant hub node116. For other topologies, e.g., star topology, bus topology, and ringtopology, the spanning tree protocol (STP) may be used in order toprevent looping of data packets in the data network.

FIG. 2 shows an exemplary, non-limiting CSME data network, designated200, that is deployed in a tree topology. As illustrated, the CSME datanetwork 200 includes a hub node 202 and a redundant hub node 204. Aplurality of aggregator nodes 206 is connected to the hub node 202 in atree configuration. In other words, aggregator nodes 206 can beconnected to the hub node 202 and other aggregator nodes 206 can beconnected to each of these aggregator nodes 206. This pattern can berepeated and the branches of the “tree” can grow more complex. Asfurther shown in FIG. 2, one or more aggregator nodes 206 can also beconnected to the redundant hub node 204 in addition to the hub node 202.

Referring now to FIG. 3, a system for designing a CSME data network isshown and is generally designated 300. As illustrated in FIG. 3, thesystem 300 includes a processor 302, e.g., a desk top computer, a laptop computer, a portable digital assistant (PDA), etc. An input device304, e.g., a keyboard, a mouse, a light pen, or a scanner, is connectedto the processor 300. Further, a memory 306 is connected to theprocessor 302. In a particular embodiment, the memory can be an externalmemory or an internal memory. FIG. 3 also shows a database 308 that canbe connected to the microprocessor 302.

As further depicted in FIG. 3, the system 300 can include an outputdevice 310 that is connected to the processor. In a particularembodiment, the output device 310 is a printer. FIG. 3 further showsthat the system 300 can include a display device 312, e.g., a monitor,that is connected to the processor 302. Additionally, the system 300 caninclude a CSME data network design tool 314 within the processor 302. Ina particular embodiment, the CSME data network design tool 314 is acomputer program that is embedded within the memory 306 within theprocessor 302. The CSME data network design tool 314 includes aplurality of steps that can be performed by the processor 302 in orderto design a CSME data network.

FIG. 3 also illustrates several inputs 316 that can be input to theprocessor, particularly the CSME data network design tool 314. Theinputs 316 can be used by the CSME data network design tool 314 todesign a CSME data network. In an illustrative embodiment, the inputs316 can include data network state and fiber topology information 318.The data network state and fiber topology information 318 can includefiber topology information, such as the number of spare nodes anddistance information between nodes. Further, the data network state andfiber topology information 318 can also include a list of centraloffices that can be used for aggregation nodes.

As indicated in FIG. 3, the inputs 314 to the CSME data network designtool 306 also include customer demand information 318. In a particularembodiment, the customer demand information 318 includes the number andaggregate bandwidth of customers for each serving wire center. In anillustrative embodiment, the inputs 314 to the CSME data network designtool 306 can include configuration and cost information 320 that caninclude types of data network elements, e.g., a 7609 with 4 port cardsor 16 port cards, etc. Further, the configuration and cost information320 can include equipment cost, line card cost, fiber cost, etc.

FIG. 3 further shows that the CSME data network design tool 306 caninclude a plurality of outputs 322. In a particular embodiment, theoutputs 322 can include a list of line cards for aggregation nodes 324,e.g., line cards that need to be deployed in existing aggregation nodes.Further, the outputs 322 can include a list of new aggregation nodes328. Also, the outputs 322 can include configuration information 328 forthe new aggregation nodes. In a particular embodiment, the outputs 322can also include connection information 330, e.g., port level connectioninformation for the new equipment. The port level connection informationindicates how to interconnect particular port numbers on particular linecards of particular nodes. FIG. 3 further indicates that the outputs 322can include cost information 332, e.g., total cost of equipment and abreakdown of those costs by equipment type.

FIG. 4 shows an exemplary, non-limiting embodiment of a method fordesigning a CSME data network. Commencing at block 400, embedded datanetwork information is input to the design tool. In a particularembodiment, the embedded data network information can be used to build acurrent data network state and fiber topology. The fiber topology can beextracted from a trunk integrated record keeping system (TIRKS). Also,the configuration and connection pattern of the existing core andaggregation nodes can be extracted from an element management system(EMS). Next, at block 402, customer demand information is input to thedesign tool. At block 404, equipment information is input to the designtool. Moving to block 406, one or more design constraints are input tothe design tool. For example, the design constraints can include amaximum allowable distance between two aggregation nodes or a maximumamount of data traffic through a particular aggregation node.

Proceeding to block 408, a multicast tree topology without redundancy islocated within the existing nodes. In an illustrative embodiment, the“root” of the tree topology is located at a predetermined hub node andthe “leaves” of the tree topology are located at one or more customerlocations, i.e., access nodes. FIG. 5, discussed in detail below,illustrates an algorithm for locating the multicast tree within theexisting nodes. Referring back to FIG. 4, at block 410, an aggregationnode is placed at the hub of the multicast tree and the redundant hub ofthe multicast tree. At block 412, an aggregation node is placed at otherappropriate locations in the multicast tree. FIG. 6 illustrates a methodfor determining where to locate other aggregation nodes in the multicasttree topology. The aggregation-to-aggregation links created during thedesign of the non-redundant tree topology can be considered primarylinks.

Moving to block 414, the availability for each aggregation location inthe tree is computed. The availability is a measure of how much datatraffic that a particular aggregation node can handle. At decision step416, a decision is made in order to ascertain whether the availabilityis less than a predetermined threshold. If the availability is less thanthe predetermined threshold, the logic moves to block 418 and aredundant link is added from the aggregation location to the hub node.In a particular embodiment, redundancy can be added to the previouslynon-redundant tree topology using the method shown in FIG. 7. The logicthen proceeds to block 420. If the availability is greater than thethreshold at decision step 416, the logic also proceeds to block 420. Atblock 420, each primary link is sized by dividing the aggregate customerbandwidth in the corresponding sub-tree by the concentration ratio.

In an illustrative embodiment, each redundant link is sized to carry oneunit of traffic. For example, in a gigabit Ethernet data network, eachredundant link is sized to carry one gigabit per second of traffic.Proceeding to block 422, the detailed configuration of each aggregationnode in the data network is determined. Thereafter, at block 424, thecost of the data network design is determined. At block 426, the cost ofthe data network design is output. The logic then ends at state 428.

FIG. 5 shows an exemplary, non-limiting embodiment of a method forlocating a multicast tree. Beginning at block 500, M is defined as themulticast tree. At block 502, C is defined as the set of customer nodesin the data network. Moving to block 504, the multicast tree isinitialized to contain the hub node. Thereafter, a decision step 506, adetermination is undertaken in order to ascertain whether C is empty. IfC is empty, the logic moves to decision step 518, described below. If Cis not empty, the logic moves to block 510 and a node is selected thathas the minimum distance to M. At step 512, a decision is made in orderto determine whether there are two or more nodes that are equidistant toM. If there are not two or more nodes that are equidistant to M, thenode from C is added to the multicast tree, M, at block 514. Conversely,if two or more nodes are equidistant to M, the logic moves to block 516and one of the equidistant nodes is randomly selected. Then, continuingto block 514, the randomly selected node from the set C is added to themulticast tree, M. From block 514, the logic returns to decision step506 and again, a decision is made in order to determine whether C isempty.

As stated above, if C is determined to be empty, at decision step 506,the logic proceeds to decision step 518 and a determination is made inorder to determine whether the redundant hub is part of the multicasttree. If yes, the method ends at state 508. On the other hand, if theredundant hub is not part of the multicast tree, the closest node in thetree to the redundant hub is located. At block 522, the redundant hub isadded to the tree via the branch having the closest node to theredundant hub. The logic then ends at state 508.

Referring now to FIG. 6, an exemplary, non-limiting embodiment of amethod for determining where to place aggregation nodes in the multicasttree is shown and commences at block 600. At block 600, the costsassociated with placing an aggregation node at a particular location aredetermined. Moving to block 602, the costs associated with fiber hubbingcustomers to the parent node of the aggregation node referenced in step600 are determined. The parent node of a particular node is the firstnode in the path from the particular node to the hub node that is eithera servicing wire center for a customer, the first node in the path fromthe particular node to the hub node that has a nodal degree greater thantwo nodes, or both. Next, at decision step 604, a determination is madein order to ascertain whether the fiber hubbing costs are greater thanthe aggregation costs. If the fiber costs are greater, the logic movesto block 606 and an aggregation node is placed at the particularlocation for which costs were determined in block 600 and block 602. Thelogic then ends at block 608. On the other hand, if the fiber costs areless than the aggregation costs, the customer is hubbed to the parentnode of the aggregation node 610, e.g., using fiber optic cable. Thelogic then ends at state 608.

Referring to FIG. 7, an exemplary, non-limiting method embodiment foradding redundancy to the multicast tree is shown and commences at block700 with a do loop wherein while not all of the aggregation nodes havebeen marked redundant, the following steps are performed. At block 702,the node in the tree that is closest to the hub is located. Then, atblock 704, the path, P, from that node to its parent node is determined.At block 706, the node is connected to the next closest node other thanits “parent node” by a path that is node diverse from P. Thereafter, atblock 708, that node is marked, or otherwise flagged by the CSME datanetwork design tool, as being redundant. Moving to decision step 710, adetermination is made in order to ascertain if the last non-redundantnode has been reached. If so, the logic ends at state 712. Otherwise,the logic returns to block 702 and continues for the node that is nextclosest to the hub.

With the configuration of structure described above, the system andmethod for designing a customized switched metro Ethernet data networkprovides a software tool for automatically designing a switched metroEthernet data network based on a plurality of inputs to the softwaretool. Particularly, the tool first locates a non-redundant tree topologyand then, adds redundancy as needed, e.g., based on the availability ofthe aggregation nodes. During the design of the switched metro Ethernetdata network, a number of different data can be computed, e.g., trafficintensity along different paths, so that network design issues, such asload balancing may be handled accordingly.

The design tool described also provides an automated, substantiallytransparent, and auditable method for designing CSME data networks.Further, the design tool can allow a user to perform sensitivityanalysis of a particular CSME data network design based on trafficforecasts, equipment prices, and fiber prices. A network design outputby the design tool includes a completely drawn network topology thatincludes the locations of all customer nodes, hub nodes, aggregatornodes, and core nodes. Further, the completely drawn network topologyincludes the locations of all primary and secondary connections, fiberlengths of the connections, and card provisioning for all routers andswitches. A user, e.g., a network engineer, can determine if the networkdesign output by the design tool is a feasible design. In other words,the network engineer can determine whether design meets requiredequipment constraints, it can handle all traffic demand, and it meetsone or more network availability requirements. Further, a networkengineer can determine if a feasible design is optimal by determiningwhether the network design incurs the lowest total cost.

The above-disclosed subject matter is to be considered illustrative, andnot restrictive, and the appended claims are intended to cover all suchmodifications, enhancements, and other embodiments, which fall withinthe true spirit and scope of the present invention. Thus, to the maximumextent allowed by law, the scope of the present invention is to bedetermined by the broadest permissible interpretation of the followingclaims and their equivalents, and shall not be restricted or limited bythe foregoing detailed description.

1. A computerized method for automatically designing a switched metroEthernet data network, the method comprising: receiving, at a computersystem including a computer processor and a computer readable memoryaccessible to the computer processor, data network information;receiving, at the computer system, customer demand information;receiving, at the computer system, equipment information; receiving, atthe computer system, at least one design constraint; and automaticallyestablishing and storing within the computer readable memory of thecomputer system a potential topology design for the switched metroEthernet data network at least partially based on the data networkinformation, the customer demand information, the equipment information,the at least one design constraint, or a combination thereof, wherein anew aggregation node is added at a central office that is locatedbetween a plurality of customer nodes and a parent node of the centraloffice in the potential topology design when costs associated withequipment to be added at the central office are less than costsassociated with fiber hubbing the plurality of customer nodes to theparent node of the central office.
 2. The method of claim 1, wherein thepotential topology design for the switched metro Ethernet data networkis a tree topology that is rooted at a hub node and that has a pluralityof leaves, each leaf being located at a customer location.
 3. The methodof claim 2, further comprising: locating an aggregation node with thehub node.
 4. The method of claim 3, further comprising: locating anaggregation node with a redundant hub node.
 5. The method of claim 4,further comprising: locating an aggregation node in at least one otherlocation in the tree topology.
 6. The method of claim 5, whereinplacement of the aggregation node at the at least one other location inthe tree topology is determined by: determining a first cost of locatingthe aggregation node at the at least one other location in the treetopology; determining a second cost of connecting the at least one otherlocation in the tree topology to a parent node of the aggregation nodethat could potentially be placed at the at least one other location; andlocating the aggregation node at the at least one other location in thetree topology when the second cost is greater than the first cost. 7.The method of claim 5, further comprising: computing an availabilityvalue for each aggregation node in the tree topology other than the hubnode and the redundant hub node; and adding a redundant path from theaggregation node to the hub node when the availability value is lessthan a predetermined threshold.
 8. The method of claim 7, wherein theredundant path is added by: determining a first path from a particularnode to a parent node of the particular node; and connecting theparticular node to a next closest node other than the parent node by asecond path that is different from the first path.
 9. A computerizedmethod for designing a switched metro Ethernet data network, the methodcomprising: establishing and storing, within a computer readable memoryaccessible to a computer processor of a computer system, a non-redundanttree topology for a switched metro Ethernet data network at leastpartially within a set of existing nodes; at least partially based on anavailability constraint, adding at least one redundant connection to thenon-redundant tree topology; and adding a new aggregation node at acentral office that is located between a plurality of customer nodes anda parent node of the central office in the non-redundant tree topologywhen costs associated with equipment to be added at the central officeare less than costs associated with fiber hubbing the plurality ofcustomer nodes to the parent node of the central office.
 10. The methodof claim 9, wherein the non-redundant tree topology is located based ondata network information, customer demand information, equipmentinformation, at least one design constraint, or a combination thereof.11. The method of claim 10, wherein the data network informationincludes at least one of the following: a number of spare nodes,distance information between nodes, locations of core nodes, location ofaggregation nodes, configurations of core nodes, configurations ofaggregation nodes, port-level connection information, and a list ofcentral offices that can be used for aggregation nodes.
 12. The methodof claim 10, wherein the customer demand information includes anaggregate bandwidth of customers for at least one serving wire center.13. The method of claim 10, wherein the equipment information includesat least one of the following: configuration information, costinformation, and model information.
 14. The method of claim 10, whereinthe at least one design constraint is at least one of the following: adistance between two aggregation nodes and an amount of data trafficthrough a particular aggregation node.
 15. The method of claim 14,wherein the non-redundant tree topology is determined by: initializingthe non-redundant tree topology to contain a hub node; locating a firstcustomer node within a set of customer nodes that is closest to the hubnode; connecting the first customer node to the hub node; locating asecond customer node within the set of customer nodes that is nextclosest to the hub node; and connecting the second customer node to thehub node.
 16. The method of claim 9, wherein the at least one redundantconnection is added to the non-redundant tree topology by: determining afirst path from a customer node to a parent node of the customer node;and connecting the customer node to a next closest node other than theparent node by a second path that is different from the first path. 17.A system for automatically designing a switched metro Ethernet datanetwork, the system comprising: a computer processor; a computerreadable memory accessible to the computer processor; and a computerprogram embedded within the memory for designing a switched metroEthernet data network, the computer program comprising: instructions toreceive one or more user inputs related to the switched metro Ethernetdata network; instructions to generate a non-redundant tree topology forthe switched metro Ethernet data network at least partially based on theone or more user inputs; instructions to add a new aggregation node at acentral office that is located between a plurality of customer nodes anda parent node of the central office in the non-redundant tree topologywhen costs associated with equipment to be added at the central officeare less than costs associated with fiber hubbing the plurality ofcustomer nodes to the parent node of the central office; instructions toadd one or more redundant connections to the non-redundant tree topologyto create a design; and instructions to output at least one designoutput related to the design.
 18. The system of claim 17, wherein theone or more user inputs include data network information, customerdemand information, equipment information, at least one designconstraint, or a combination thereof.
 19. The system of claim 18,wherein the data network information includes at least one of thefollowing: a number of spare nodes, distance information between nodes,locations of core nodes, location of aggregation nodes, configurationsof core nodes, configurations of aggregation nodes, port-levelconnection information, and a list of central offices that can be usedfor aggregation nodes.
 20. The system of claim 18, wherein the customerdemand information includes an aggregate bandwidth of customers for atleast one serving wire center.
 21. The system of claim 18, wherein theequipment information includes at least one of the following:configuration information, cost information, and model information. 22.The system of claim 18, wherein the at least one design constraint is atleast one of the following: a distance between two aggregation nodes andan amount of data traffic through a particular aggregation node.
 23. Thesystem of claim 17, wherein the at least one design output includes atleast one of the following: a list of line cards for existingaggregation nodes, a list of new aggregation nodes, configurationinformation for existing and new aggregation nodes, connectioninformation for existing and new aggregation nodes, and costinformation.
 24. The system of claim 17, wherein the instructions togenerate the non-redundant tree topology for the switched metro Ethernetdata network comprise: instructions to initialize a tree topology tocontain a hub node; instructions to locate a first customer node withina set of customer nodes that is proximate to the hub node; andinstructions to connect the first customer node to the hub node.
 25. Thesystem of claim 24, wherein the instructions to generate thenon-redundant tree topology for the switched metro Ethernet data networkfurther comprise: instructions to locate a second customer node withinthe set of customer nodes that is next proximate to the hub node; andinstructions to connect the second customer node to the hub node. 26.The system of claim 17, wherein the instructions to add one or moreredundant connections to the non-redundant tree topology comprise:instructions to determine a first path from a customer node to a parentnode of the customer node; and instructions to connect the customer nodeto a next closest node other than the parent node by a second path thatis different from the first path.
 27. A switched metro Ethernet datanetwork, comprising: at least one hub node; a plurality of customernodes connected to the at least one hub node to establish a treetopology; wherein: a design of the tree topology is generated using aswitched metro Ethernet data network design tool, the switched metroEthernet data network design tool comprising: instructions to generate anon-redundant tree topology for the switched metro Ethernet data networkat least partially based on one or more user inputs; instructions to adda new aggregation node at a central office that is located between theplurality of customer nodes and a parent node of the central office inthe non-redundant tree topology when costs associated with equipment tobe added at the central office are less than costs associated with fiberhubbing the plurality of customer nodes to the parent node of thecentral office; and instructions to add one or more redundantconnections to the non-redundant tree topology to create the design. 28.The switched metro Ethernet data network of claim 27, wherein the designis based on one or more user inputs to the switched metro Ethernet datanetwork design tool.
 29. The switched metro Ethernet data network ofclaim 28, wherein the switched metro Ethernet data network design toolfurther comprises: instructions to initialize a tree topology to containthe at least one hub node; instructions to locate a first customer nodewithin the plurality of customer nodes that is proximate to the at leastone hub node; and instructions to connect the first customer node to theat least one hub node.
 30. The switched metro Ethernet data network ofclaim 29, wherein the switched metro Ethernet data network design toolfurther comprises: instructions to locate a second customer node withinthe plurality of customer nodes that is next proximate to the at leastone hub node; and instructions to connect the second customer node tothe at least one hub node.
 31. The switched metro Ethernet data networkof claim 30, wherein the switched metro Ethernet data network designtool further comprises: instructions to determine a first path from acustomer node to a parent node of the customer node; and instructions toconnect the customer node to a next closest node other than the parentnode by a second path that is different from the first path.